1. Field of the Invention
This invention relates generally to shaft seals and more particularly to a multiple ring shaft seal with enhanced fluid return.
2. Related History
In instances where rotating shafts projected through housings and wherein fluid, carried on one side of the housing was to be excluded from the other side of the housing, shaft seals were employed between the housing and the shaft to permit rotation of the shaft and preclude passage of the fluid. When rotating shafts were supported by oil lubricated journal bearings, the fluid carried in the housing was a lubricating oil and the housing was configured with an oil return sump for recirculation of the oil.
A typical environment of an oil lubricated journal bearing with shaft seals between a rotating shaft, carried by the bearing, and a housing included operating machinery, for example, blower or compressor shafts.
Among the drawbacks associated with prior oil seals was their inability to effectively seal their rotating shafts and/or preclude leakage between the seal outer periphery and the housing within which the seals were seated.
While seals have been provided with a plurality of axially spaced sealing rings which defined oil collection channels, such seals suffered from inefficient oil return systems, especially with respect to the channels axially spaced from the interior of the housing. The oil return systems generally comprised individual bores with inadequate flow characteristics. The inefficiency of prior oil return systems resulted not only in leakage around the shaft but in oil overheating, especially in environments wherein gravity flow was impeded, e.g. when the axis of the shaft and seal was not fixed in a horizontal plane.
Other problems encountered with prior seals related to the fact that their operation was not axially reversible, that is, seals included an inner axial face and an outer axial face and improper seating in housings was to be avoided.
Further disadvantages of prior shaft seals included the inability to effectively prevent oil, sprayed from the rotating shaft to the interior of the housing, from dripping back on the shaft and entering the seal.